| # This implements the "diagnose-unwind" command, usually installed |
| # in the debug session like |
| # command script import lldb.diagnose |
| # it is used when lldb's backtrace fails -- it collects and prints |
| # information about the stack frames, and tries an alternate unwind |
| # algorithm, that will help to understand why lldb's unwind algorithm |
| # did not succeed. |
| |
| import optparse |
| import lldb |
| import re |
| import shlex |
| |
| # Print the frame number, pc, frame pointer, module UUID and function name |
| # Returns the SBModule that contains the PC, if it could be found |
| |
| |
| def backtrace_print_frame(target, frame_num, addr, fp): |
| process = target.GetProcess() |
| addr_for_printing = addr |
| addr_width = process.GetAddressByteSize() * 2 |
| if frame_num > 0: |
| addr = addr - 1 |
| |
| sbaddr = lldb.SBAddress() |
| try: |
| sbaddr.SetLoadAddress(addr, target) |
| module_description = "" |
| if sbaddr.GetModule(): |
| module_filename = "" |
| module_uuid_str = sbaddr.GetModule().GetUUIDString() |
| if module_uuid_str is None: |
| module_uuid_str = "" |
| if sbaddr.GetModule().GetFileSpec(): |
| module_filename = sbaddr.GetModule().GetFileSpec().GetFilename() |
| if module_filename is None: |
| module_filename = "" |
| if module_uuid_str != "" or module_filename != "": |
| module_description = '%s %s' % ( |
| module_filename, module_uuid_str) |
| except Exception: |
| print '%2d: pc==0x%-*x fp==0x%-*x' % (frame_num, addr_width, addr_for_printing, addr_width, fp) |
| return |
| |
| sym_ctx = target.ResolveSymbolContextForAddress( |
| sbaddr, lldb.eSymbolContextEverything) |
| if sym_ctx.IsValid() and sym_ctx.GetSymbol().IsValid(): |
| function_start = sym_ctx.GetSymbol().GetStartAddress().GetLoadAddress(target) |
| offset = addr - function_start |
| print '%2d: pc==0x%-*x fp==0x%-*x %s %s + %d' % (frame_num, addr_width, addr_for_printing, addr_width, fp, module_description, sym_ctx.GetSymbol().GetName(), offset) |
| else: |
| print '%2d: pc==0x%-*x fp==0x%-*x %s' % (frame_num, addr_width, addr_for_printing, addr_width, fp, module_description) |
| return sbaddr.GetModule() |
| |
| # A simple stack walk algorithm that follows the frame chain. |
| # Returns a two-element list; the first element is a list of modules |
| # seen and the second element is a list of addresses seen during the backtrace. |
| |
| |
| def simple_backtrace(debugger): |
| target = debugger.GetSelectedTarget() |
| process = target.GetProcess() |
| cur_thread = process.GetSelectedThread() |
| |
| initial_fp = cur_thread.GetFrameAtIndex(0).GetFP() |
| |
| # If the pseudoreg "fp" isn't recognized, on arm hardcode to r7 which is |
| # correct for Darwin programs. |
| if initial_fp == lldb.LLDB_INVALID_ADDRESS and target.triple[0:3] == "arm": |
| for reggroup in cur_thread.GetFrameAtIndex(1).registers: |
| if reggroup.GetName() == "General Purpose Registers": |
| for reg in reggroup: |
| if reg.GetName() == "r7": |
| initial_fp = int(reg.GetValue(), 16) |
| |
| module_list = [] |
| address_list = [cur_thread.GetFrameAtIndex(0).GetPC()] |
| this_module = backtrace_print_frame( |
| target, 0, cur_thread.GetFrameAtIndex(0).GetPC(), initial_fp) |
| print_stack_frame(process, initial_fp) |
| print "" |
| if this_module is not None: |
| module_list.append(this_module) |
| if cur_thread.GetNumFrames() < 2: |
| return [module_list, address_list] |
| |
| cur_fp = process.ReadPointerFromMemory(initial_fp, lldb.SBError()) |
| cur_pc = process.ReadPointerFromMemory( |
| initial_fp + process.GetAddressByteSize(), lldb.SBError()) |
| |
| frame_num = 1 |
| |
| while cur_pc != 0 and cur_fp != 0 and cur_pc != lldb.LLDB_INVALID_ADDRESS and cur_fp != lldb.LLDB_INVALID_ADDRESS: |
| address_list.append(cur_pc) |
| this_module = backtrace_print_frame(target, frame_num, cur_pc, cur_fp) |
| print_stack_frame(process, cur_fp) |
| print "" |
| if this_module is not None: |
| module_list.append(this_module) |
| frame_num = frame_num + 1 |
| next_pc = 0 |
| next_fp = 0 |
| if target.triple[ |
| 0:6] == "x86_64" or target.triple[ |
| 0:4] == "i386" or target.triple[ |
| 0:3] == "arm": |
| error = lldb.SBError() |
| next_pc = process.ReadPointerFromMemory( |
| cur_fp + process.GetAddressByteSize(), error) |
| if not error.Success(): |
| next_pc = 0 |
| next_fp = process.ReadPointerFromMemory(cur_fp, error) |
| if not error.Success(): |
| next_fp = 0 |
| # Clear the 0th bit for arm frames - this indicates it is a thumb frame |
| if target.triple[0:3] == "arm" and (next_pc & 1) == 1: |
| next_pc = next_pc & ~1 |
| cur_pc = next_pc |
| cur_fp = next_fp |
| this_module = backtrace_print_frame(target, frame_num, cur_pc, cur_fp) |
| print_stack_frame(process, cur_fp) |
| print "" |
| if this_module is not None: |
| module_list.append(this_module) |
| return [module_list, address_list] |
| |
| |
| def print_stack_frame(process, fp): |
| if fp == 0 or fp == lldb.LLDB_INVALID_ADDRESS or fp == 1: |
| return |
| addr_size = process.GetAddressByteSize() |
| addr = fp - (2 * addr_size) |
| i = 0 |
| outline = "Stack frame from $fp-%d: " % (2 * addr_size) |
| error = lldb.SBError() |
| try: |
| while i < 5 and error.Success(): |
| address = process.ReadPointerFromMemory( |
| addr + (i * addr_size), error) |
| outline += " 0x%x" % address |
| i += 1 |
| print outline |
| except Exception: |
| return |
| |
| |
| def diagnose_unwind(debugger, command, result, dict): |
| """ |
| Gather diagnostic information to help debug incorrect unwind (backtrace) |
| behavior in lldb. When there is a backtrace that doesn't look |
| correct, run this command with the correct thread selected and a |
| large amount of diagnostic information will be printed, it is likely |
| to be helpful when reporting the problem. |
| """ |
| |
| command_args = shlex.split(command) |
| parser = create_diagnose_unwind_options() |
| try: |
| (options, args) = parser.parse_args(command_args) |
| except: |
| return |
| target = debugger.GetSelectedTarget() |
| if target: |
| process = target.GetProcess() |
| if process: |
| thread = process.GetSelectedThread() |
| if thread: |
| lldb_versions_match = re.search( |
| r'[lL][lL][dD][bB]-(\d+)([.](\d+))?([.](\d+))?', |
| debugger.GetVersionString()) |
| lldb_version = 0 |
| lldb_minor = 0 |
| if len(lldb_versions_match.groups() |
| ) >= 1 and lldb_versions_match.groups()[0]: |
| lldb_major = int(lldb_versions_match.groups()[0]) |
| if len(lldb_versions_match.groups() |
| ) >= 5 and lldb_versions_match.groups()[4]: |
| lldb_minor = int(lldb_versions_match.groups()[4]) |
| |
| modules_seen = [] |
| addresses_seen = [] |
| |
| print 'LLDB version %s' % debugger.GetVersionString() |
| print 'Unwind diagnostics for thread %d' % thread.GetIndexID() |
| print "" |
| print "=============================================================================================" |
| print "" |
| print "OS plugin setting:" |
| debugger.HandleCommand( |
| "settings show target.process.python-os-plugin-path") |
| print "" |
| print "Live register context:" |
| thread.SetSelectedFrame(0) |
| debugger.HandleCommand("register read") |
| print "" |
| print "=============================================================================================" |
| print "" |
| print "lldb's unwind algorithm:" |
| print "" |
| frame_num = 0 |
| for frame in thread.frames: |
| if not frame.IsInlined(): |
| this_module = backtrace_print_frame( |
| target, frame_num, frame.GetPC(), frame.GetFP()) |
| print_stack_frame(process, frame.GetFP()) |
| print "" |
| if this_module is not None: |
| modules_seen.append(this_module) |
| addresses_seen.append(frame.GetPC()) |
| frame_num = frame_num + 1 |
| print "" |
| print "=============================================================================================" |
| print "" |
| print "Simple stack walk algorithm:" |
| print "" |
| (module_list, address_list) = simple_backtrace(debugger) |
| if module_list and module_list is not None: |
| modules_seen += module_list |
| if address_list and address_list is not None: |
| addresses_seen = set(addresses_seen) |
| addresses_seen.update(set(address_list)) |
| |
| print "" |
| print "=============================================================================================" |
| print "" |
| print "Modules seen in stack walks:" |
| print "" |
| modules_already_seen = set() |
| for module in modules_seen: |
| if module is not None and module.GetFileSpec().GetFilename() is not None: |
| if not module.GetFileSpec().GetFilename() in modules_already_seen: |
| debugger.HandleCommand( |
| 'image list %s' % |
| module.GetFileSpec().GetFilename()) |
| modules_already_seen.add( |
| module.GetFileSpec().GetFilename()) |
| |
| print "" |
| print "=============================================================================================" |
| print "" |
| print "Disassembly ofaddresses seen in stack walks:" |
| print "" |
| additional_addresses_to_disassemble = addresses_seen |
| for frame in thread.frames: |
| if not frame.IsInlined(): |
| print "--------------------------------------------------------------------------------------" |
| print "" |
| print "Disassembly of %s, frame %d, address 0x%x" % (frame.GetFunctionName(), frame.GetFrameID(), frame.GetPC()) |
| print "" |
| if target.triple[ |
| 0:6] == "x86_64" or target.triple[ |
| 0:4] == "i386": |
| debugger.HandleCommand( |
| 'disassemble -F att -a 0x%x' % frame.GetPC()) |
| else: |
| debugger.HandleCommand( |
| 'disassemble -a 0x%x' % |
| frame.GetPC()) |
| if frame.GetPC() in additional_addresses_to_disassemble: |
| additional_addresses_to_disassemble.remove( |
| frame.GetPC()) |
| |
| for address in list(additional_addresses_to_disassemble): |
| print "--------------------------------------------------------------------------------------" |
| print "" |
| print "Disassembly of 0x%x" % address |
| print "" |
| if target.triple[ |
| 0:6] == "x86_64" or target.triple[ |
| 0:4] == "i386": |
| debugger.HandleCommand( |
| 'disassemble -F att -a 0x%x' % address) |
| else: |
| debugger.HandleCommand('disassemble -a 0x%x' % address) |
| |
| print "" |
| print "=============================================================================================" |
| print "" |
| additional_addresses_to_show_unwind = addresses_seen |
| for frame in thread.frames: |
| if not frame.IsInlined(): |
| print "--------------------------------------------------------------------------------------" |
| print "" |
| print "Unwind instructions for %s, frame %d" % (frame.GetFunctionName(), frame.GetFrameID()) |
| print "" |
| debugger.HandleCommand( |
| 'image show-unwind -a "0x%x"' % frame.GetPC()) |
| if frame.GetPC() in additional_addresses_to_show_unwind: |
| additional_addresses_to_show_unwind.remove( |
| frame.GetPC()) |
| |
| for address in list(additional_addresses_to_show_unwind): |
| print "--------------------------------------------------------------------------------------" |
| print "" |
| print "Unwind instructions for 0x%x" % address |
| print "" |
| debugger.HandleCommand( |
| 'image show-unwind -a "0x%x"' % address) |
| |
| |
| def create_diagnose_unwind_options(): |
| usage = "usage: %prog" |
| description = '''Print diagnostic information about a thread backtrace which will help to debug unwind problems''' |
| parser = optparse.OptionParser( |
| description=description, |
| prog='diagnose_unwind', |
| usage=usage) |
| return parser |
| |
| lldb.debugger.HandleCommand( |
| 'command script add -f %s.diagnose_unwind diagnose-unwind' % |
| __name__) |
| print 'The "diagnose-unwind" command has been installed, type "help diagnose-unwind" for detailed help.' |
